Basic unit processor for offset plates and method of processing them

ABSTRACT

An automatic self-contained basic unit-processor for an offset photolithographic plate which may be used, at different times, for any processing step requiring contacting of the plate by liquid. For example, an exposed plate is developed by contacting the exposed surface of the plate with the conventional developing fluid, and subjecting the surface to a linear, reciprocating rubbing action by a sponge. This rubbing action produces results surprisingly similar to those produced by a manual rotary action. A fully assembled basic-unit processor of this invention requires only that it be connected to a source of power, and to a reservoir for recirculatable processing fluid. A single electric motor is adapted (a) to drive each roll of two pairs of coupled drive rolls, (b) to reciprocate a sponge in frictional contact with a generally horizontal offset plate, and (c) to supply a controllable flow rate of fluid for processing the plate. Rotary movement of the electric motor effects positive rotation of each of a pair of coupled drive rolls, in opposite directions with respect to each other, to negate slipping of a wet plate between them. Translation of rotary movement of the electric motor in a first plane to linear reciprocation in a second plane essentially orthogonal to the first, is effected by a direct rod-actuated drive with swivel rod-ends. The fully assembled basic-unit processor may be used sequentially for various functions, e.g. developing, washing and gumming. It may also be transported through a standard 36-inch wide doorway, eliminating the drawbacks characteristic of machines which are to be assembled at the installation site.

CROSS REFERENCE TO RELATED CASES

This application is a division of applicant's copending application,Ser. No. 386,510 filed Aug. 8, 1973.

BACKGROUND OF THE INVENTION

Though the occasional user of photo-lithographic plates may stillprocess an exposed plate manually, the large-scale commercialutilization of offset plates has made automatic processing of theseplates an economic necessity. Moreover, it is well-known that chemicalsutilized in the processing of offset plates may be notably injurious tohumans and due care must be exercised to prevent harm resulting fromexposure to the chemicals.

Manual processing of an exposed offset plate comprises pouring asufficient quantity of developer on the plate and working the developerover the area of the plate until a dense, even image appears. If thedeveloper expends itself before the plate is fully developed, moredeveloper is added. If the developer becomes tacky, water is added tothe sponge to restore a desirable consistency to the developer. Afterthe plate is developed, it is flushed with water and excess water isthen removed, as for example, with a squeegee. This method of manualdevelopment is essentially the same irrespective as to whether theprocess is an additive or subtractive process. The developed plate maythereafter be "gummed" if desired, to preserve the plate.

The continuation of manual processing of plates with currently availablechemicals is being legislatively discouraged by requirements ofgovernment agencies relative to the use of dangerous chemicals, whichrequirements place severe limitations as to the acceptability ofprocessing plates manually, that is, without breathing some of thevapors or permitting accidental contact of the chemicals.

Again, chemicals used in processing offset plates are notably difficultto dispose of because of their toxic effect on living matter in theenvironment.

Stricter enforcement of laws with respect to discarding chemicals intoconventional sewer systems places a high value on a recirculating andholding tank for chemicals. Thus it is highly desirable to utilize anintegrated or self-contained machine in which the chemicals may berecirculated to depletion, prior to being disposed of in a suitablemanner.

The foregoing combination of circumstances dictates the use of anautomatic self-contained basic-unit processor even for the economicallyhandicapped user of offset plates.

The foregoing remarks are directed equally to additive type andsubtractive type developing machines such as are conventionally used atpresent in the printing industry. They are more particularly directed tosubtractive type developing machines. Machines specifically adapted toprocess exposed-lithographic plates automatically are disclosed in U.S.Pat. Nos. 3,608,464; 3,593,641; 3,589,261; 3,562,834; 3,448,720; andothers.

Unlike prior art machines, the basic-unit processor of this inventionperforms only a single process function at any one time. This apparentlimitation affords the unit exceptional versatility as a basic-unitcapable of being used as a developer or a coater; as a developer it maybe used for subtractive or additive developers; as a coater it may beused for coating a metal plate with a photosensitive material, or forcoating a developed offset plate with "gum."

The coating of aluminum plates with a wipe-on diazo coating has been arelatively recent development. Initially, and in a few instances whereonly a very few plates are to be coated, the diazo coating fluid ispoured onto a plate and wiped more or less evenly over the surface witha clean, lintless cloth. The plate is thereafter dried. This manualcoating of aluminum plates has been superceded by an automatic coaterwherein a pair of coupled drive rolls is disposed above the surface ofthe coating fluid, with the lower roll partially submerged in thecoating fluid. A plate to be coated is fed to the rolls, generallyface-downwards, and the rotation of the lower roll picks up apre-determinable quantity of fluid which is deposited on the face of theplate, thus coating it. Often this method of coating a sheet isunsatisfactory, and the sheet is then run a second time, to recoat thesheet. It is believed that rerunning the sheet redissolves part of thecoating and negates the effect of entrapped air bubbles and dirtparticles which may have been incorporated in the first coating.

Another coating machine which purports to eliminate the problems of airbubble and dirt particle entrapment, includes a brush with a back andforth motion, in combination with the drive rolls of the aforementionedprior art machine. In each of the prior art machines the basic problemof slippage of a wet plate between a pair of coupled drive rolls,remains. In operation, attempts to overcome the slippage problem includeincreasing the pressure on the drive rolls. Increasing the pressure onthe drive rolls is not only detrimental to the surface of the rolls, butalso makes it more difficult to provide an even coating. Particularlywhere a diazo coating fluid is utilized, the chemical action of thefluid tends to harden the rolls and complicates the problem of obtaininga uniform coating on the plate. The results obtained with the basic-unitprocessor are different from those obtained with prior art machines andthis difference in results would not be expected by one skilled in theart.

In addition to being useful as a coater for sensitizing a plate, thebasic-unit processor of this invention may be used with equal facilityas a developer of exposed offset plates, whether the plates are to bedeveloped additively or subtractively, and as a washing apparatus fordeveloped offset plates. Finally, the basic-unit processor may again beused as a coater for sealing or gumming the washed plate. Each of theforegoing functions of the basic-unit processor is discharged with onlya change of processing fluid and simple changes in operationnecessitated by the process fluid used. Moreover, each function isdischarged utilizing a rectilinear reciprocating motion of the rubbingmeans and a positive sychronous drive for drive rolls in each pair ofdrive rolls through which the plate is transferred. It is well-knownthat a rubbing action is essential for coating and developing plates,and prior art devices have variously utilized rotary, orbital andrectilinear rubbing motions. Surprisingly, rectilinear reciprocation isfound to be the most advantageous rubbing motion which is equallyeffective for any basic step in the processing of an offset plate.

From a practical point of view, the more successful machines whether forcoating or for developing offset plates are relatively large andenormously complicated. Not unexpectedly, these require a capitalinvestment which precludes their acquisition and operation by a smalluser of plates. With respect to size, it is noted that availablemachines, for plates from about 25 inches to about 33 inches in width,will not pass, fully assembled, through a standard 36-inch wide doorwayand consequently must be assembled at the installation site, preferablyby a qualified factory representative. Similarly, a factory-trainedmaintenance person is generally required to diagnose and rectifymalfunctions of prior art machines because the complicatedinterrelationship of moving parts and a large number of electricalcircuits precludes maintenance by persons normally employed in aprinting shop. Thus there has been a growing need for a simple,inexpensive, and safe-to-use automatic plate processor which will notonly be easy to acquire and easy to maintain, but which will not bedetrimental to the disposal systems conventionally used for sewagetreatment. Above all there is a well-established need for a smallbasic-unit processor which is versatile, and mechanically as ruggedlyreliable as its results are, from a printer's viewpoint, routinelyreproducible. This invention is directed to such a need.

SUMMARY OF THE INVENTION

It is therefore a general object of this invention to provide a new andimproved apparatus which may be used selectively and at the option ofthe user, for coating, developing, washing and/or gumming a lithographicplate and the like.

It is another general object of this invention to provide an apparatusfor the aforementioned treatment of a plate, which apparatus isself-contained and does not flow used or other processing fluids, waterand the like, or other contaminants into a sewer or other disposalsystem.

It is another general object of this invention to provide a new andimproved apparatus for converting rotary motion about a first axis intorotary motion of two pairs of coupled drive rolls, each drive roll ofeach pair being driven positively in the opposite direction to eachother.

It is another general object of the instant invention to provide amachine which emulates the process results of a manual wipe-on motionfor spreading a photo-sensitive coating on a metal plate, and a manualrotary movement for aiding the development of an exposed plate, with asurprisingly effective, simple rectilinear reciprocating motion of arubbing surface such as a sponge which engages the exposed surface ofthe plate in frictional sliding contact.

It is a more particular object of this invention to provide a processorwhich may be delivered to a purchaser, ready to use, requiring only thatit be connected to a source of power and a reservoir in which chemicalsfor processing a plate are recirculatably accumulated.

It is a more specific object of this invention to provide an automaticsingle stage processor for a single processing step on a lithographicplate which processor utilizes simple components co-acting in theframework of a disciplined geometry, wherein a main requirement is thata fully assembled machine be self-contained and promptly utilizable withminor adjustments, for any processing fluid.

It is another specific object of this invention to provide aself-contained integrated basic-unit processor, two or more of which maybe used in tandem for sequential processing steps, namely coating a thinmetal sheet with a photosensitive coating, developing an exposed plate,washing a developed plate, and gumming a washed plate.

It is still another specific object of this invention to provide amachine in which a single stage for contacting a metal plate with thefluid is compartmentalized by at least two pairs of coupled drive rolls,between which a reciprocating sponge provides the necessary scrubbingmotion and simultaneously minimizes the adverse effect of air bubblesand dirt particles which may be entrapped on the surface of the plate.

It is another specific object of this invention to provide a machine inwhich each drive roll of two pairs of coupled drive rolls is providedwith means for being positively driven, the upper drive rolls in onedirection, and the lower drive rolls in an opposite direction relativeto the direction of the upper drive rolls, so as to provide positive,essentially non-slip transport of a wet offset plate as it is processed.

It is a specific object of this invention to provide a self-containedbasic-unit processor wherein drive rolls are driven positively inopposite directions utilizing a dual chaindrive power-transmissionmechanism driven by a single drive means.

It is still another object of this invention to provide a basic-unitprocessor with a predetermined amount of recirculatable processingfluid.

It is still another object of this invention to provide a basic-unitprocessor in which a single motor means may be used to drive all machinefunctions.

It is also a specific object of this invention to provide a machinewhich has built-in safeguards to enable the use of difficultly handledchemicals with safety, to protect the operator of the machine whileusing them, to enable the full utilization of the chemicals, and toconfine the expended chemicals for convenient disposal.

It is another more specific object of this invention to provide adirect, uniquely adapted, rod -actuated drive for oscillating a rockerarm drivingly engaged with a sponge bar to produce the desired linearreciprocating action.

It is another specific object of the instant invention to provide amachine which may be used to feed lithographic plates in eitherdirection through the drive rolls.

A still further object of this invention is to provide a new andimproved apparatus for converting rotary motion about a first axis intolinear reciprocating motion along a second axis in transversely spacedrelationship with said first axis, and simultaneously into rotarymotion, of coupled drive rolls each in a direction opposite relative tothe other about a third axis in spaced apart parallel relationship withsaid first axis, a new and improved automatic processor for offsetplates utilizable as a basic-unit processor either by itself or inconjunction with a stacker, gumming machine, or other plate processingapparatus, a new and improved chain-drive for utilizing a single rotarymeans to drive all machine functions, a new and improved variabledispensing pump to provide necessary chemistry, and a new and improvedprocess for developing either coating an offset plate, or for an exposedoffset plate, each of which obtains one or more of the objects andadvantages set forth hereinabove.

These and other objects, features and advantages of the processor ofthis invention will become apparent to those skilled in the art from thefollowing description of preferred forms thereof, reference being had tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the drive mechanism of the basic-unitprocessor of this invention.

FIG. 2 is a perspective plan view of the processing deck and the directrod-actuated drive for reciprocating the sponge bar.

FIG. 3 is an elevation view, partly broken away, of the right side ofthe processor showing the direct rod-actuated drive for reciprocatingthe sponge bar.

FIG. 4 is a perspective view, partly broken away, of the right side ofthe processor viewed from one end of the machine, where an offset plateis fed into a first pair of coupled drive rolls.

FIG. 5 is an elevation view, partly broken away, of the left side of theprocessor showing the dual chain-drive mechanism for utilizing therotary motion of a single motor means to provide the necessary positivedrives for each of the drive rolls.

FIG. 6 is an elevation perspective view of the in-feed end of thebasic-unit processor.

FIG. 7 is a perspective view, partly broken away, of a rocker plate inthe direct rod-actuated drive.

In the figures of the drawing, like reference numerals are used todenote like parts. Some of the parts are dimensionally exaggerated forclarity of illustration and to facilitate the description of the drivemeans and the manner in which it benefits the operation of the automaticprocessor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

According to the present invention, the automatic basic-unit processorof this invention may be used either as a `developer` to develop or as a`coater` to coat an exposed offset plate. As a developer, it may be usedto develop either additive or subtractive photosensitive layers, and ascoater it may be used to coat a metal plate with a photosensitive layer,or an exposed and developed offset plate with a protective gumcomposition. It will be apparent from this description hereinafter thatthis basic-unit processor may not be used to discharge more than one ofthe foregoing functions simultaneously; in other words, while it isbeing used to develop an offset plate it cannot be used to coat theplate, and vice versa. However, this basic-unit processor may be usedfirst to coat a metal plate with a desired photosensitive layer, and,after a suitable change of chemicals, then used to develop an exposedoffset plate, and finally, after still another change of chemicals, thenused to `gum` the developed plate. In practice, a multiplicity of platesmay be run sequentially and serially for each particular operation ofsensitizing, developing and gumming the plates.

It is to be noted that, particularly where chemicals for subtractivedeveloping are used, it is desirable to discharge developed plates intoa wash tank or sink in which the plates are washed with water withoutbeing manipulated manually. This procedure minimizes the exposure of theoperator to the processing chemicals used. For convenience, thebasic-unit processor may be mounted on a wheeled carriage or on rollersfor ease of movement to and from the sink, as required.

The basic-unit processor of this invention is a self-contained,single-operation processor having a recirculatable process-chemicalssupply. Preferably, the process-chemicals for each operation aresupplied from a holding tank within the basic-unit processor. However,in those instances where one basic-unit processor is to be used for oneor more operations in a more or less fixed location, it may be desirableto provide one or more holding tanks, as necessary, located apart fromthe processor, but provided with means to connect them for use,recirculatably. Of course, it is not a necessary element of theapparatus of this invention that the chemicals used in each operation berecirculatable, but it will be evident that failure to recirculatecostly chemicals is not only economically unjustifiable but ecologicallyundesirable. In a preferred embodiment, the basic-unit processor and theholding tank are transportable as a unit, the tank being connected forprocessing a plate and recirculating the process chemicals (sometimesalso referred to as the "chemistry"). The basic-unit processor isreadied for use simply by connecting it to a suitable source of power.

This basic-unit processor, and details of its construction and operationwill hereinafter be described in relation to the subtractive developmentof an offset plate utilizing chemicals which are generally easier tomaintain in homogeneous dispersion than conventional additive developingchemicals. It will be recognized that in an analogous manner, bysubstituting the appropriate chemistry, the unit may be used as anadditive developer, a coater for sensitizing a plate, a gummingapparatus, or simply for washing a plate with water.

Referring now to FIGS. 1, 2 and 5, there is illustrated a self-containedbasic-unit processor indicated generally at 1, with covers 2, to protect(a) a chain drive mechanism, indicated generally at 3, for receiving,transporting and discharging an an exposed offset plate 4, (b) a spongebar assembly or applicator means indicated generally at 5, adapted toreciprocably rub the exposed surface of the plate, (c) pump means,indicated generally at 6, for supplying process-chemicals to berecirculated, (d) a holding tank 7 for the chemicals, and (e) drivemeans, as will be described hereinafter, for operating (a), (b) and (c).The basic-unit processor is preferably readied for operation by placingit so as to discharge each processed offset plate into a sink, forreasons explained hereinbefore, and connecting a power cable from theprocessor to a source of electric current (details not shown). Thelength of the processor in the direction of travel of a plate is lessthan 36 inches, with all the covers 2 in position, and the machine fullyassembled. This dimension permits the basic-unit processor to betransported through a standard 36-inch doorway.

Processing chemicals, for example Lydel, such as are well-known in theart for subtractively developing an exposed offset plate, are containedin the holding tank 7. The container in which the chemicals are soldserves as a convenient holding tank which may be removably disposed in astructural framework 8. The framework 8 which is disposed on rollers, orother means 11 (FIG. 6) includes a drive deck 12 on which a firstreduction gear means 13, an electric motor or other drive means 14, avariable speed drive indicated generally at 15, and a second reductiongear means 16 are operatively disposed. The variable speed drive 15 isdrivingly engaged with a pump indicated generally at 6, which isconveniently disposed below the deck 12.

Referring now more particularly to FIG. 2, there is indicated a plateprocessing deck indicated generally at 21, which is provided withsuitable openings 22 through which process chemicals may drain into adrain-pan 23 (See FIG. 1). Process chemicals are conducted to theprocess deck from the pump 6 by a discharge line 24 and a distributiontube (not shown) through which the chemicals are distributed evenly overthe surface of an exposed plate to be developed. The plate 4 enters theprocess deck 21 through a first pair of coupled in-feed drive rolls 26at the feed end or in-feed end of the basic-unit processor. Theprocessor is normally operated by a person facing the in-feed end. Thechain drive mechanism 3 is disposed on the left hand side or rear of themachine, and the sponge bar assembly 5 is drivingly engaged with adirect rod-activated drive, indicated generally at 27, disposed on theright hand side or front of the machine.

A second pair of coupled out-feed drive rolls 28 are disposed at theout-feed or discharge end of the processor. Each pair of coupled driverolls is adapted to receive a plate therebetween, and to urge the platetherethrough. Moreover, as will be explained hereinafter, each driveroll of each pair of drive rolls is positively rotated, preferablysynchronously, that is at essentially the same speed, so as to permit anessentially non-slip transfer of a wet plate which is pressingly engagedbetween each pair of drive rolls.

The sponge bar assembly 5 is disposed intermediate the in-feed andout-feed drive rolls and essentially coplanarly therewith. The spongebar assembly comprises a bar 31 which extends across the process deck21. The bar 31 supports a channel 32 in which an elongated sponge isremovably disposed by any suitable means such as prongs (not shown). Anyresilient rubbing means may be used, but a sponge, whether natural orsynthetic, is preferred. The sponge is so disposed as to be infrictional sliding contact with the plate to be processed.

One end of the bar 31, on the right hand side of the processor, isdisposed between a pair of guides 30, and the other end of the bar 31 issimilarly disposed between another pair of guides (not shown) tofacilitate rectilinear reciprocation of the bar. The right hand end ofthe bar 31 is provided with a cam follower block 35 adapted to engage acam 36. It has been found that this particular relationship of cam andcam follower, rather than vice versa, provides a rectilinear movement ofthe sponge coplanarly with the surface of the plate 4 to be processedthus permitting even, frictional sliding contact of the sponge acrossthe plate. The cam 36 is fixedly disposed in a rocker plate 37 (See FIG.7) fixedly disposed on one end of a shaft 38. A pin 39 is also fixedlydisposed on the rocker plate 37 and located so that the cam 36 and thepin 39 are equidistant from the end of the shaft on which the rockerplate 37 is mounted. The shaft 38 is rotatably disposed in a rollerbearing 42 mounted in a pillow block 43 against the right side of thestructural framework of the processor. In the embodiment illustratedherein, single sponge bar assembly 5 is used, however, this is not meantto limit the invention in that manner.

The pin 39 has journalled thereupon a swivel rod-end 44 adjustablydisposed at one end of a rod means 45. Another swivel rod-end 46 isadjustably disposed at the other end of the rod 45 and journalled upon astub shaft 47 which projects from a crankarm 48 rotatable about ahorizontal axis. Rotation of the crankarm 48 produces a back and forthrocking or oscillating motion of the rocker plate 37 about an axistransversely spaced from, but not parallel with, the axis of rotation ofthe crankarm. It will be evident, that to obtain the rectilinearreciprocation of the sponge bar assembly in the plane desired, withsimplicity, the axes referred to are preferably perpendicular to oneanother.

It will be recognized that swivel rod-ends are desirable to accomodateangulation of the rod 45 which otherwise would `bind` thus permittingnon-parallelogramatic motion to be imparted, utilizing direct rod means.Other means may be used for this purpose, such as, for example, aflexible rod with predetermined rigidity, so chosen as to flex to theextent necessary to permit angulated motion of the flexible rod whichmay utilize conventional, fixed or non-swivelling rod-ends.Alternatively, a conventional rod with fixed rod-ends may be modified bysectioning the rod to provide at least two spring-connected sections. Afixed rod end on one section may be pivotally disposed on the pin 39 anda fixed rod end may be pivotally disposed on the stubshaft 47, so thatthe spring between the sections accomodates angulation of the rodsections and transmits a copressive, pushing force.

Referring now to FIG. 3, each drive roll of the in-feed and out-feeddrive roll pairs is fixedly disposed on a shaft 50, each end of which isjournalled in upper bearing blocks 51-U and lower blocks 51-L mounted inthe right and left sides of the structural framework 8. The upperbearing blocks 51-U have an oval shaped surface with the oppositesurfaces being so adapted as to permit adjustment of the relativepressure exerted between each pair of drive rolls. This is convenientlyeffected by a pressure adjusting means such as a bolt 52 threadedlydisposed in a support bar 53. A lock-nut 54 is provided to lock the bolt52 at any desired roller pressure. Similar pressure adjusting means areprovided for each upper roll and the drive rolls are readied foroperation by setting the rolls to exert an even pressure therebetween.Other pressure adjusting means such as a wedge or cam may be used also.

Referring now to FIG. 5, it is seen that the left hand side ends of thedrive roll shafts 50 protrude through upper and lower bearing blocks51-U and 51-L respectively in a manner analogous to the right-hand sidebearing blocks described hereinbefore in FIG. 3. Each shaft endprotrudes sufficiently to permit sprocket means to be fixedly disposedthereupon. The upper in-feed drive roll has a sprocket 56 keyed thereto;the lower in-feed drive roll has a sprocket 57 keyed thereto; the upperout-feed drive roll has a sprocket 58 keyed thereto; the lower out-feeddrive roll has a sprocket 59 keyed thereto. Instead of sprockets,pulleys may be used, or any other means which may be adapted forpositive rotation. Sprockets are preferred for ruggedness, precision andreliability. It will be noted that each sprocket is rotatable in a planeparallel to and spaced apart from the other sprocket in each pair. Thisspacing results from the fact that the diameter of each drive roll isrelatively smaller than the diameter of the sprockets, and permits theupper drive rolls to be driven in a forward plane and the lower rolls tobe driven in a rear plane.

The upper drive roll sprockets 56 and 58 are driven by a forward drivechain 62 drivingly trained thereupon and the lower drive roll sprockets57 and 59 are driven by a rear drive chain 63 drivingly trainedthereupon. Both chains 62 and 63 are drivingly trained upon a dual drivesprocket 64 keyed to the shaft of the reduction gear drive means 16 (SeeFIG. 1). Additionally, a front idler sprocket 65 and a rear idlersprocket 66 are rotatably disposed for rotation in the front and rearplanes respectively. The front chain 62 is drivingly trained on thefront row of teeth of a dual sprocket 64, and sprockets 65, 56 and 58 soas to produce a clockwise rotation of all sprockets when the dualsprocket 64 is rotated in a clock-wise direction. The rear chain 63 isdrivingly trained on the rear row of teeth of the dual sprocket 64 sothat, with the same clock-wise rotation, sprockets 66, 57 and 59 aredriven in a counter-clockwise direction. In the particular embodimentdescribed herein, all sprockets are 17-pitch sprockets so as to driveboth upper and lower drive rolls at the same speed. This configurationof sprockets may be used to drive any driven elements where oppositerotation of positively driven elements is desired. In the instantbasic-unit processor this dual chain-drive mechanism permits a wetoffset plate to be received by and urged through coupled drive rollswith essentially no slip between the plate and the drive rolls.

Referring again to FIG. 1, it will be seen that the electric motor 14,by itself, provides the drive means for all drive functions of thebasic-unit processor. The shaft of the motor 14 is provided with asheave 71 which is wide enough to accomodate two timing belts 72 and 73in side-by-side relationship thereupon. The belt 72 drivingly engages asheave 74 of the reduction gear means 13 and effects rotation of thecrankarm 48. The timing belt 73 drivingly engages a sheave 75 of thevariable speed drive means 15, such as is commercially available fromBrowning, which includes a spring-loaded sheave 76 and a manuallycontrolled sheave 77 drivingly engaged with a V-belt 78. The manualsheave 77 is adjusted for a desired speed by means of a control knob 79(See FIG. 6) at the in-feed end of the processor.

The variable drive means 15 is also provided with a sheave 81 which isdrivingly engaged, by means of a V-belt 82, with a sheave 83. The sheave83 operates the pump means 6 and supplies process chemicals forprocessing a plate on the process deck. When a basic-unit processor isused for a single specific operation, say developing with a particularsubtractive developer, the ratio of the diameters of sheaves 81 and 83is chosen to provide the optimum flow rate of developer. Where, on theother hand, the basic-unit processor is used for several functions, orwith developers which require different flow rates, the sheave 81 isreplaced with a spring-loaded sheave similar to the sheave 76 and thesheave 83 is replaced with a manually controlled sheave similar tosheave 77. It will be understood that the ratio of pulleys for such asubstitution will be such as to permit the desired range of pumpingrates by a contol knob in an analogous manner as with control knob 79.

The foregoing description refers to a single basic-unit processor whichmay be used selectively, at the option of the user, for any one ofseveral processing steps to which a lithographic plate is subjected. Therate at which the plate is fed through a basic-unit processor and therate of flow of processing fluids depends on the particular processingstep for which the basic-unit is used, the choice of processing fluidand the particular characteristics of the plate being processed. Ifdesired a basic-unit processor may be used in combination with a dryerif drying is necessary.

Where two or more processing steps are to be carried out sequentiallytwo or more basic-unit processors may be used in tandem. For example afirst basic-unit may be used to coat a metal plate with a photosensitivelayer, a second basic-unit may be used to develop an exposedlithographic plate, a third basic-unit may be used to wash the plate anda fourth unit may be used to gum the washed plate. It will be apparentthat any combination of processing steps may be practiced using pluralbasic-unit processors in tandem.

Modifications, changes and improvements to the preferred forms of theinvention herein disclosed, described and illustrated may occur to thoseskilled in the art who come to understand the principles and preceptsthereof. Accordingly, the scope of the patent to be issued hereon shouldnot be limited to the particular embodiments of the invention set forthherein, but rather should be limited by the advance by which theinvention has promoted the art.

What is claimed is:
 1. Apparatus comprising first and second drive rollmeans having spaced parallel axes and being paired for simultaneousengagement with material passing therebetween, and means to positivelydrive each said drive roll means in a direction opposite to the other;said last named means comprising a drive shaft means in spaced, parallelrelation with said axes of said drive roll means, sprocket means mountedon said drive shaft means, sprocket means on each said drive roll means,first and second continuous flexible drive means engaging and driven bysaid drive shaft sprocket means, one said flexible drive means engagingsaid sprocket means on one said drive roll means and the other saidflexible drive means engaging the said sprocket means on the other saiddrive roll means, said flexible drive means driving said first andsecond drive roll means in opposite directions, and means to rotate saiddrive shaft means.
 2. The apparatus according to claim 1, in which saidfirst and second flexible drive means engage said drive shaft sprocketmeans in angularly spaced relationship whereby to be moved in oppositedirections thereby.
 3. The apparatus according to claim 2 in which atleast one said flexible drive means engages idler means whereby thedirection of the reach but not the movement thereof is changed.
 4. Theapparatus according to claim 1 with a plurality of spaced pairs ofsimilar first and second drive roll means, said first flexible drivemeans driving one said drive roll means of each pair, said secondflexible drive means driving the other said drive roll means of eachsaid pair.